The invention relates to methods, apparatus and software products for determining a set of properties of a target object in an environment. Illustrative examples of the target object include a person, animal, vehicle, instrument, shopping cart or project folder. An illustrative example of the target device property set includes location. An illustrative but non-restrictive application of the invention involves locating a wireless mobile terminal in a wireless communication environment, such as in a wireless local-area network (WLAN) or cellular network.
U.S. Pat. No. 6,393,294 to Luis Perez-Breva et al. discloses a representative prior art technique for locating a mobile unit in wireless communication system. The location of a remote mobile unit is determined by comparing a snapshot of a predefined portion of the radio-frequency spectrum taken by the mobile unit to a reference database containing multiple snapshots taken at various locations. Thus this technique, like many others, is based on a comparison of signal parameter observations at the mobile device's location with a database of calibrated or simulated parameters at several known locations.
Conventional techniques have problems in modelling the target object's movement. Many conventional techniques model the target object's movement by a number of states. Increasing the number of possible states increases the number of state transitions rapidly, which consumes memory and causes a high computational load.